Indium tin oxide ITO is a solid solution of indium (III) oxide (In2O3) and tin (IV) oxide (SnO2), typically 90%/10% by weight. ITO is electrically conductive, optically transparent, and colorless in thin layers. Because this particular combination of material attributes is quite rare, the value of ITO for use in numerous electronics applications that can utilize this combination of attributes is notably high. Deposition techniques used for ITO include electron beam evaporation, physical vapor deposition, and sputter deposition.
ITO is used as a transparent conductive oxide (TCO) electrode layer in electronic devices such as organic light emitting diodes, photodetectors, silicon photovoltaics, organic photovoltaics (OPV), liquid crystal displays, plasma displays, touch panels, antistatic coatings and electromagnetic interference shielding, among others. The popularity of these electronic devices has lead to a consistent and significant growth in sales of these devices, which has lead to a rapidly growing demand for ITO material. This rapidly growing demand has lead to rapid increases in the cost of the ITO materials and to a growing concern in the industry about this cost growth and newly emerging performance problems.
ITO has several economic and performance problems that require resolution, however. The first economic problem is that indium is a precious metal that has undergone price escalation over recent years as its use has increased dramatically in comparison to the amount of ITO that is available. A second economic problem is that the deposition process for most product applications utilizing ITO is accomplished by way of expensive vacuum sputtering methods.
One performance problem is that ITO can be relatively brittle, which makes it relatively difficult to use ITO on flexible circuit material. Given that one important growth potential for ITO is in electronic components that make extensive use of flexible electronic substrates, this will become a growing problem. Another performance problem is the=relative inefficiency in the conversion of electrons into photons in ITO applications for OLEDS. In an OLED application, light is trapped in the ITO layer due to its higher refractive index in comparison to the organic materials. This results in less than 25% of the generated photons actually coming out of the device and become useful.
Although many devices and techniques for providing conductive and transparent layers in electronics applications have generally worked well in the past, there is always a desire to provide alternatives for such layers. In particular, what is desired are conductive and transparent layers having a lower cost, better performance, and greater ease of manufacturability than traditional ITO layers.